Within a few hours they will be appear (after a sync). Typically this is not an issue, since in reality, Promotions are updated in advance and the following forced differential sync (that runs daily) will pick them up.
In order to successfully load the large amount of Items selected for a Promotion (due to NetSuite Defect 374161), we had to defensively change the way these larger Item Level Promotions are processed. In doing so, NetSuite manages the caching differently (for performance reasons) and uses the cache for a period of time (out of our control).
Once NetSuite addresses the defect, we will revert back to the way this should be handled.